1. Technical Field
This invention relates generally to dynamic oil seals of the type for creating a fluid tight seal between a rotating shaft and a housing.
2. Related Art
Dynamic radial shaft oil seals are designed to have a so-called “oil-side” of the seal and an “air-side.” These designations pertain to the orientation of the seal when installed, with the oil-side facing the interior of the housing and in communication with the oil, whereas the air-side faces outwardly and is exposed to the air.
During use, while maintaining an effective seal, it is desirable to keep dust and other contaminants on the air-side of the seal while maintaining lubrication on the oil-side of the seal. It is known to incorporate a static band on a sealing surface of a seal lip with spiral grooves extending from the static band toward an oil-side of the seal to pump lubrication back to the oil-side of the seal. However, with the spiral grooves merging with the static band, at least some of the lubrication, rather than being pumped back to the oil-side of the seal, can bypass the static band, where it tends to remain on the air-side of the static band. This has undesirable affects on the seal by potentially allowing a negative pressure to develop inside the seal and the lubrication to build up on the airside of the static band, which in turn can cause deposits to form and ultimately cause the spiral grooves on the oil-side of the static band to lose their ability to return lubrication back to the oil-side of the seal. Accordingly, the useful life of the seal, and possibly the useful life of bearings or other components that the seal is protecting, is reduced.